Low pulsation pump

ABSTRACT

The object of the present invention is to provide a centrifugal pump or compressor which reduces pulsations and variations in pressure, commonly called “pump noise”. This invention discloses a centrifugal pump design wherein the relationship of the impeller to the volute shape and the exit port tend to decrease the net amplitude of the pulsations within the flow of pressurized fluid produced by cancellation of pulse peaks.

FIELD OF THE INVENTION

[0001] This invention relates to an improved centrifugal pump or compressor which reduces or eliminates pulsations and variations in pressure, commonly called “pump noise”.

BACKGROUND OF THE INVENTION

[0002] In the field of ornamental fountains and particularly ornamental fountains which utilize highly laminar streams of water, the slight pulsations or variations in pressure, sometimes referred to as “pump noise”, observed in the pressurized flow from centrifugal water pumps, is undesirable and tends to diminish the smooth flow of water, or the degree of laminarity which may otherwise be achieved.

[0003] In a typical centrifugal pump, a small number of blades on the impeller and a relatively narrow exit port tends to be highly efficient regarding head pressure and flow rate for a given power consumption. However, for applications where pulsations are objectionable this configuration tends to be unsatisfactory.

[0004]FIG. 1 illustrates a two-bladed impeller centrifugal pump 10 having an impeller an impeller 11 and exit port 12 of 45 degrees. In such a pump when impeller blades 1 and 2 pass by the exit port 12, each tends to produce a distinct pressure spike 14, 16, above the mean pump pressure, which lasts for the length of time required for the respective blades 1 and 2 to pass by the exit port 12. In this example there is a pulse of 45 degrees duration every 180 degrees as shown in FIG. 1A.

[0005]FIG. 2 shows a pump 20 having an impeller 21 having four blades 22, 23, 24 and 25; and a 45 degree exit port 29. In this case as shown in FIG. 2A the respective pressure pulsations 26, 27, 28, and 29 resulting from blades 25, 22, 23 and 24 above the mean pump head pressure are 45 degrees in duration and occur every 90 degrees.

[0006]FIG. 3 shows a pump 30 having an eight-bladed impeller 31, 32, 33, 34, 35, 36, 37, 38 and a 45 degree port 39, resulting in 45 degree pulses 41, 42, 43, 44, 45, 46, 47, 48, occurring every 45 degrees.

SUMMARY OF THE INVENTION

[0007] The object of the present invention is to provide a centrifugal pump or compressor which reduces pulsations and variations in pressure, commonly called “pump noise”. This invention discloses a centrifugal pump design wherein the relationship of the impeller to the volute shape and the exit port tend to decrease the net amplitude of the pulsations within the flow of pressurized water produced by cancellation of pulse peaks.

THE DRAWINGS

[0008]FIG. 1 is a schematic side elevation view of a prior art centrifugal pump having two blades.

[0009]FIG. 1A is a plot of pulse peaks against angle of rotation of pump in FIG. 1.

[0010]FIG. 2 is a schematic side elevation view of a prior art centrifugal pump having four blades.

[0011]FIG. 2A is a plot of pulse peaks against angle of rotation of the pump in FIG. 2.

[0012]FIG. 3 is a schematic side elevation view of a prior art centrifugal pump having eight blades.

[0013]FIG. 3A is a plot of pulse peaks against angle of rotation of the pump in FIG. 3.

[0014]FIG. 4 is a schematic side elevation view of the present invention centrifugal pump having eight blades, and an elongated exit port of about 100 degrees.

[0015]FIG. 4A is a plot of pulse peaks against angle of rotation of the pump in FIG. 4 showing the cancellation of pulse peaks in accordance with the invention.

[0016]FIG. 5 is a side elevation view of a centrifugal pump or compressor in accordance with the present invention.

[0017]FIG. 6 is a sectional view of FIG. 5 looking in the direction of the arrows along the line 6-6 in FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0018]FIG. 4 discloses a pump 49 wherein an impeller 50 with a relatively large number of blades, at least five blades, with eight shown 51, 52, 53, 54, 55, 56, 57, 58, is matched with an enlarged exit port 60 so that two or more impeller blades are passing by the exit port at any given time. In the configuration disclosed in FIG. 4 the eight-bladed impeller 50 is matched to an 100 degree exit port 60 resulting in pulses 71, 72, 73, 74, 75 76, 77, 78, of 100 degrees duration that are generated every 45 degrees so that the peak of the pulse 71 generated by blade 51 approximately coincides with the respective troughs 81, 82, 83, 84, 85, 86, 87, between pulses 78 & 72, 71 & 73, 72, & 74, 73 & 75, and 74 & 76, 75, & 77. In other words, multiple pulses are set in timing and duration so that they tend to cancel each other out.

[0019]FIG. 5 discloses a pump 90 with an impeller shaft 94, riding in bearing and seal assembly 95. Securely fastened to the end 93 of shaft 94 is the impeller 92, shown with eight blades 98. The shaft 94, bearing and seal assembly 95, and impeller 92, are shown mounted within pump housing 100, with inlet port 101, an outlet pipe 106, and internal volute surface 108, with an exit port 107.

[0020] In use, whenever the impeller shaft 94 is made to turn on a clockwise direction as shown in FIG. 6 by some an external power source (not shown), it will turn the impeller, 92. If the pump cavity 110, has been previously flooded, then the moving impeller blades, 98, will tend to throw the fluid outward by means of centrifugal force creating a lower pressure (suction) in the inlet port 101, and a higher pressure in the exit port 107, thus creating a pumping action.

[0021] With two or more impeller blades concurrently passing by the exit port 107 at all times, the pressure pulsations above the mean pump head pressure will each tend to be 100 degrees of impeller 92, rotation in duration and will occur with each blade, 98, passing by the exit port, 107, that is, with each 45 degrees of impeller, 92, rotation.

[0022] Thus the pressure pulsations produced will tend to overlay each other and will tend to cancel each other out. Even though an eight bladed impeller, 92, and a 100 degree exit port, 107, are used for illustration, this principle of self canceling pulsations will be effective for any impeller with a large number of blades (five or more) combined with an elongated exit port which is large enough so that two or more blades are passing by it at any given time. 

What is claimed is:
 1. An improved centrifugal pump which reduces or eliminates pulsations and variations in pressure, comprising: a centrifugal pump having a body portion having an internal volute surface; said pump also having an impeller with a plurality of blades; said pump also having an elongated exit port having an enlarged discharge angle; and wherein the relationship of said impeller to said volute shape and said exit port tend to decrease the net amplitude of the pulsations within the flow of pressurized fluid produced at said exit port.
 2. An improved centrifugal pump according to claim 1 wherein the pressure pulsations produced tend to overlay each other and tend to cancel each other out.
 3. An improved centrifugal pump according to claim 3 wherein two or more of said blades are passing by said exit port at one time.
 4. An improved centrifugal pump according to claim 2 wherein said compressor has at least five blades.
 5. An improved centrifugal pump according to claim 4 wherein said exit port has an angle of at least 100 degrees.
 6. An improved centrifugal pump according to claim 4 wherein said impeller has at least five blades and not more then eight blades.
 7. An improved centrifugal pump according to claim 5 wherein said impeller has eight blades, and wherein said exit port has an angle of at least 100 degrees.
 8. An improved centrifugal pump according to claim 6 wherein said impeller has eight blades, and wherein said exit port has an angle of about 100 degrees.
 9. An improved centrifugal pump according to claim 4 wherein said pump includes an impeller shaft having a shaft end and extends within a bearing and seal assembly.
 10. An improved centrifugal pump according to claim 9 wherein said impeller fastened to said shaft end.
 11. An improved centrifugal pump according to claim 10 wherein said shaft, said bearing and seal assembly and said impeller are mounted within a pump housing.
 12. An improved centrifugal pump according to claim 11 wherein said housing includes an inlet port, said internal volute surface, an exit port and an outlet conduit. 